# system

From cppreference.com
< c‎ | program

Defined in header ``<stdlib.h>`` |  |
int system( const char *command ); |  |

Calls the host environment's command processor with the parameter `command`. Returns an implementation-defined value (usually the value that the invoked program returns).

If command is a null pointer, checks if the host environment has a command processor and returns a nonzero value if and only if the command processor exists.

### Parameters

command | - | character string identifying the command to be run in the command processor. If a null pointer is given, command processor is checked for existence

### Return value

Implementation-defined value. If `command` is a null pointer, returns a nonzero value if and only if the command processor exists.

### Notes

On POSIX systems, the return value can be decomposed using `WEXITSTATUS` and `WSTOPSIG`.

The related POSIX function popen makes the output generated by `command` available to the caller.

### Example

In this example there is a system call of the unix command date +%A and a system call to (possibly installed) gcc compiler with command-line argument (--version):

Run this code

    #include <stdlib.h>

    int main(void) {
        system("date +%A");
        system("gcc --version");
    }

Possible output:

    Wednesday
    gcc (GCC) 11.2.0
    ...

### References

- C17 standard (ISO/IEC 9899:2018):

  - 7.22.4.8 The system function (p: 257)

- C11 standard (ISO/IEC 9899:2011):

  - 7.22.4.8 The system function (p: 353-354)

- C99 standard (ISO/IEC 9899:1999):

  - 7.20.4.6 The system function (p: 317)

- C89/C90 standard (ISO/IEC 9899:1990):

  - 4.10.4.5 The system function

### See also

C++ documentation for system

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